Up to 500 jobs are to go as a result of the collapse of Bothwell-based civil engineering group WJ Harte.

Both WJ Harte and subsidiary firm RJT Pennant were placed in administration on Wednesday evening and all 720 staff employed by the group were sent home.

Around 200 staff have been retained to complete work currently on the group's order book.

The construction union UCATT warned of problems at the company on Monday after receiving a substantial number of calls from employees who had been sent home from the Bothwell plant.

UCATT believed the company was close to calling in administrators after it failed in a bid to extend its credit facility.

Anne Buchanan, joint interim manager of the Harte Group and corporate recovery partner with administrator PKF, said: "Harte Group is a long established, highly regarded firm servicing the construction industry.

"The firm has experienced a severe reduction in turnover over the last few years as well as considerable levels of bad debt from creditors who themselves have gone bust.

"Despite shedding jobs over the last few years to cope with this decline in turnover the firm is now unable to continue trading.

"The downturn in the construction sector means that the business is no longer able to operate and, unfortunately as a consequence, around 500 of the employees within the Harte Group are being made redundant.

"To put this in context the latest Scottish corporate insolvency statistics showed that 138 businesses in the construction sector went under in the first three quarters of 2011 compared with 158 for the whole of 2010 and just 72 in 2009.

"The increase incorporate failures related to construction businesses is increasing which indicates continuing problems for the sector."

Buchanan added: "It is unfortunate that this company, which has been around for so long and traded profitably for much of that time, should be closed down due to a number of factors.

"The long term effect of the closure of a business like this may have a serious impact on the recovery of the construction sector in the future.

"A separate company, RJT Excavations Limited, is not part of the current administration process."

WJ Harte was founded in 1974 andspecialises in providing engineering services to housebuilders.